Variable packet lengths for high packet data rate communications

ABSTRACT

Method and apparatus for variable length Physical Layer (PL) packet generation. Multiple Security Layer (SL) packets may be multiplexed into a single PL packet to increase efficiency, wherein the SL packets may have variable lengths. In one embodiment, different format SL packets for different users are combined into capsules that form the PL packet. Shorter packets are for users in poor channel conditions or requiring smaller amounts of data due to the applications and the accompanying Quality of Service (QoS) requirements. In one embodiment, a modified Preamble structure provides for Unicast or multi-user packets. Alternate embodiment provides modified Rate Sets, a mechanism for identifying ACK from a single-user packet or a multiplexed packet (delayed ACK). ON/OFF keying for ACK channel v/s bi-polar keying used in IS-856, and/or multi-valued interpretation of DRC.

BACKGROUND 1. Field

[0001] The present invention relates generally to communication systems,and more specifically to variable packet lengths for application to ahigh rate packet data communications.

2. Background

[0002] High Packet Data Rate (HPDR) communications are optimized forbulk data transport. One HPDR system is detailed in the cdma2000,standard referred to as 1xEV-DO and specified in TIA/EIA IS-856 entitled“cdma2000 High Rate Packet Data Air Interface Specification.” FIG. 1illustrates the air interface layering architecture for a 1° x.EV-DOsystem. The Connection layer (CL) provides air link connectionestablishment and maintenance services. The Security Layer (SL) providesencryption and authentication services. The Physical Layer (PL) providesthe channel structure, frequency, power output, modulation and encodingspecifications for the Forward and Reverse channels. The Medium AccessControl (MAC) layer defines procedures to receive and transmit over thePhysical Layer. FIG. 2 illustrates the Forward channel structure,including Pilot, MAC, Control and Traffic channels.

[0003] Data is processed as illustrated in FIG. 1, wherein processing ofa Connection Layer (CL) packet 102 includes first adding a securitylayer header 110 and tail 112 to the form a Security Layer (SL) packet104. The SL packet 104 is then used to generate a Medium Access Control(MAC) layer packet 106, and finally a Physical Layer (PL) packet 108.The MAC layer 106 payload is a fixed number of bits. The PL 108 payloadis then a multiple n times the length of the MAC layer 106 payload, plusthe length of physical layer overhead (CRC tail bits etc.), wherein n isan integer.

[0004] The limitations of the fixed MAC layer 106 payload results ininefficiencies in transmission and thus wasted bandwidth. For example,when the channel condition to a given user is “good as determined bySignal to Interference and Noise Ratio (SINR) or Data Rate Control (DRC)measure exceeding a threshold, there is a desire to transmit largerpackets. For such a user, transmission of smaller blocks of data, suchas voice packets, vocoder frames, etc., on the current forward linkstructure in IS-856 would result in wasted space in the MAC layer 106packet. As the size of the data is much smaller than the fixed length ofthe MAC layer 106 packet, the remaining bits are filled with a padding.The result is inefficiency, as the MAC layer 106 packet is not fullyutilized.

[0005] There is a need, therefore, for a variable packet length for HRDcommunications, wherein the variable length packets provide efficiency.There is further a need to combine smaller MAC layer 106 packets into asingle physical layer packet, allowing data of multiple users to betransmitted per packet.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 is a portion of the air interface layering architecture ofa High Rate Packet Data (HRPD) communication system.

[0007]FIG. 2 is a forward channel structure for a HRPD communicationsystem.

[0008]FIG. 3 is a security layer structure for a Format A connectionlayer packet.

[0009]FIG. 43 is a security layer structure for a Format B connectionlayer packet.

[0010]FIGS. 5 and 6 illustrate the generation for simplex and multiplexMAC packets from security layer packets.

[0011]FIG. 7 is a physical layer packet structure used to carry a singleMAC layer packet of length less than 1000 bits.

[0012]FIG. 8 is a physical layer packet structure used to carry a singleMAC layer packet of length equal to 1000 bits.

[0013]FIG. 9 is a physical layer packet structure used to carry multipleMAC layer packets of length equal to 1000 bits each.

[0014]FIG. 10 is a table of nominal data rates and data rate requestinterpretations.

[0015]FIG. 11 shows the compatibility between an explicit data rateindicator and data rate request values.

[0016]FIG. 12 illustrates generation of a physical layer packet based ona short security layer packet.

[0017]FIG. 13 illustrates generation of a 512-bit multiplexed physicallayer packet containing payloads for two users.

[0018]FIG. 14 is a multiplex physical layer packet including differentlength security layer packets.

[0019]FIG. 15 is a physical layer packet including multiple mediumaccess control layer capsules.

[0020]FIGS. 16 and 17 illustrate transmission of multiple slots toachieve a nominal data rate and a maximum data rate.

[0021]FIG. 18 is an access network according to one embodiment.

[0022]FIG. 19 is an access terminal according to one embodiment.

DETAILED DESCRIPTION

[0023] The word “exemplary” is used herein to mean “serving as anexample, instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments.

[0024] An HDR subscriber station, referred to herein as an accessterminal (AT), may be mobile or stationary, and may communicate with oneor more HDR base stations, referred to herein as modem pool transceivers(MPTs). An access terminal transmits and receives data packets throughone or more modem pool transceivers to an HDR base station controller,referred to herein as a modem pool controller (MPC). Modem pooltransceivers and modem pool controllers are parts of a network called anaccess network. An Access Network (AN) transports data packets betweenmultiple access terminals (ATs). The AN includes network equipmentproviding connectivity between a packet switched data network and theAT. An AN is similar to a Base Station (BS), while an AT is similar to aMobile Station (MS).

[0025] The access network may be further connected to additionalnetworks outside the access network, such as a corporate intranet or theInternet, and may transport data packets between each access terminaland such outside networks. An access terminal that has established anactive traffic channel connection with one or more modem pooltransceivers is called an active access terminal, and is said to be in atraffic state. An access terminal that is in the process of establishingan active traffic channel connection with one or more modem pooltransceivers is said to be in a connection setup state. An accessterminal may be any data device that communicates through a wirelesschannel or through a wired channel, for example using fiber optic orcoaxial cables. An access terminal may further be any of a number oftypes of devices including but not limited to PC card, compact flash,external or internal modem, or wireless or wireline phone. Thecommunication link through which the access terminal sends signals tothe modem pool transceiver is called a reverse link. The communicationlink through which a modem pool transceiver sends signals to an accessterminal is called a forward link.

[0026] In the following discussion, the SL packet size is given as 1000bits. The SL packet includes an amount of overhead given as x bits.Alternate embodiments may provide an alternate length for the SL packet.FIG. 3 illustrates two formats for data referred to as Format A andFormat B. Format A is defined as a SL packet having a one to onerelation with the CL packet. In other words, the length of the CL packetis 1000 bits (i.e., the given size of the SL packet) minus x. In otherwords, the CL packet plus the SL overhead is equal to the given lengthof the SL packet. Format B is defined as 1) a SL packet which includespadding, or 2) a SL packet which includes multiple CL packets with orwithout padding.

[0027] According to one embodiment, the size of the SL packet may bevariable. FIG. 3 illustrates a Format A packet wherein the SL packet isone of four sizes. The size of the SL packet may be one of: 112, 240,488, or 1000 bits. The SL is made up of the CL packet. There is one CLpacket corresponding to one user. Data is processed as illustrated inFIG. 1, wherein processing of a Connection Layer (CL) packet 102includes concatenating one or more Connection Layer packets, togetherwith padding if necessary, and then adding a security layer header 110and tail 112 to the form a Security Layer (SL) packet 104.

[0028]FIG. 4 illustrates a Format B packet wherein the SL packet isvariable, and the SL payload includes one or more CL packets pluspadding. The resultant SL packet size is one of 112, 240, 488, or 1000bits.

[0029]FIG. 5 illustrates processing of SL packets, wherein the SLpackets have a length less than 1000 bits. Two fields are appended tothe SL packet, a SubPacket Identification (SPID) or MAC index value,which is 6 bits long, and a LENgth indicator (LEN), which are two bits.The MAC index identifies the user to whom the packet is directed. TheMAC index field is used to identify the user to whom the packet isdestined. LEN specifies the format. The LEN field is used to specifywhether the SL packet is of Format A or Format B. If the SL packet is offormat A, the LEN also specifies the length of the SL packet, whichcould take on one of three values: 112, 240, 488. The resultant MAClayer subpacket is 120, 248, or 496 bits long. The MAC layer subpacketis then processed to form the MAC layer packet by determining ifmultiple MAC layer subpackets are to be combined. The MAC layer packetincludes one or more MAC layer subpackets plus an inner CyclicRedundancy Check value along with any necessary padding. The MAC layerpacket is referred to as Multiplex if containing more than one SLpacket, possibly for different users. A CRC value and a tail value areapplied to the MAC layer packet to form a PL layer packet as illustratedin FIG. 7. The resultant PL packet is then 152, 280, or 528 bits long.

[0030]FIG. 6 illustrates processing of SL packets, wherein the SLpackets have a length equal to 1000 bits. The MAC layer payload is theSL packet. The MAC layer packet is referred to as Simplex.

[0031]FIG. 8 illustrates processing of MAC layer packets wherein the MAClayer packet has a length of 1000 bits. The processing of FIG. 8 may beused for Format A or Format B SL packets. A CRC value and a tail areapplied to the MAC layer packet. Additionally, a format indicator (FMT),of 2 bits, is also applied. The significance of the FMT is given as inTable I. TABLE I Format field (FMT) Definitions 01 = Format A Simplex 11= Format B Simplex 00 = Multiplex MAC packet 10 = Invalid MAC packet

[0032] “Simplex” refers to a MAC packet with one SL packet; and“multiplex” implies more than one SL packet. In other words, a simplexMAC packet contains exactly one SL packet; and a multiplex MAC packetcontains two or more SL packets. A capsule is defined as a MAC packet,followed by a few bits of overhead, which carry information specific tothat MAC packet, e.g. FIG. 15 illustrates a single PL packet carriesmultiple MAC layer packets. A MAC capsule is used when a PL packetcarries two or more MAC packets. The capsule is used to identify theindividual capsules and is, therefore, used only in case of a multiplexpacket.

[0033] According to one embodiment, the size of the PL packet may beincreased to accommodate larger transfers. The larger PL packet alsoallows for multiple MAC packets to be embedded within one PL packet.Specifically, multiple MAC packets with multiple destination addressesmay each be embedded in a subpacket. In this way, one PL packet istransmitted to multiple users. As illustrated in FIG. 9, a capsule isgiven including a MAC layer packet, the FMT and a capsule address. Theinterpretation of the FMT field is as specified in Table 1. The capsuleaddress provides the destination of the MAC layer packet. Note that ifthe MAC layer packet is a multiplex packet, i.e., including multiple CLlayer packets each having a different destination address, the capsuleaddress may be left blank. In other words, if the PL packet will includeinformation for multiple users, then the capsule address has littlemeaning, as it may only designate one user. The capsule address is 6bits in the present example. The composite of the MAC layer packet, FMTand capsule address forms the MAC layer capsule.

[0034] Continuing with FIG. 9, multiple MAC layer capsules may beconcatenated. To the combination of MAC layer capsules is added a CRCvalue, a tail, and any necessary padding. The padding may be includedsuch that the MAC layer capsule overhead, i.e., pad, CRC and tail, has alength of 16*n bits. The specific length is a design choice, determinedby the number of bits leftover in the PL packet after the MAC capsulesand tail bits are included. Whenever there are enough bits left, it isdesirable to use 32-bit CRC. In the present example the PL packet oflength 2048 bits uses a 24-bit CRC, while longer PL packets use a 32-bitCRC. In the present example, there are four extended lengths for the PLpacket: 2048, 3072, 4096 and 5120 bits.

[0035]FIG. 10 is a table of nominal data rates corresponding to theextended PL packets, which are recently defined with respect to HRPD inIS-856. Referring to the PL packet lengths as given in FIG. 7, a packetlength of 152 bits is transmitted and incrementally retransmitted over 4slots, for a nominal transmission data rate of 19.2 kbps. Note thataccording to one embodiment, calculation of data rates adopts theconvention of rounding down the PL packet length to the nearest power oftwo. Each slot in a 1xEV-DO system is 1.666 ms long. For good channelconditions, the data rate may be increased to 76.8 kbps through the useof early termination. Early termination refers to a system wherein thereceiver of the data transmits an acknowledgement or ACK when the datahas been received and decoded correctly. In this way, all four attemptsmay not be used for transmission. Such acknowledgement terminates anyfurther transmission of the packet. Similarly, packet lengths of 280 and528 bits are each transmitted over 6 slots, resulting in nominal datarates of 25.6 kbps, and 57.6 kbps, respectively. Similarly, each mayhave a maximum data rate of 153.6 kbps, and 307.2 kbps, respectively,given early termination.

[0036] Referring to FIG. 16, for 152 bits per packet per slot having anominal data rate of 19.2 kbps, termination after the first slot resultsin a maximum data rate of 76.8 kbps. Early termination after the secondslot results in a maximum data rate of 38.4 kbps, or half the maximumdata rate. If all four slots are transmitted, the nominal data rate of19.2 kbps is realized.

[0037]FIG. 17 illustrates the transmission of 280 bits per packet perslot, wherein the transmission and incremental retransmission is over 6slots. Here the nominal data rate is 25.6 kbps. Termination after thefirst slot results in a maximum data rate of 153.6 kbps, whiletermination after the third slot results in a data rate of 115.2 kbps,or half the maximum. If all 6 slots are transmitted, the nominal datarate of 25.6 kbps is realized.

[0038] In a 1xEV-DO system, the AT provides a data rate request to theAN, wherein the data rate request is transmitted on the Reverse Link(RL), and specifically on a Data Request Channel (DRC). The data raterequest may be calculated as a function of the received signal qualityat the AT. The AT determines a maximum data rate at which the AT mayreceive data. The maximum data rate is then requested by the AT for datatransmissions from the AN. The data rate request is received by the AN,which then selects a packet size accordingly. For a given data raterequest, the AN may generate a shorter PL packet, a conventional PLpacket, or a longer PL packet. Each data rate request corresponds to oneor more packet sizes. This choice depends on the QoS for the flow inquestion.

[0039] For example, as given in FIG. 10, for a data rate request of 19.2kbps, referred to as “DRC0,” the AN may transmit a simplex PL packet oflength 152 bits to effect the 19.2 kbps or may transmit a PL packet oflength 280 bits for an, effective data rate of 25.6 kbps. While the AThas knowledge of the possible PL packet sizes and data rates, the ATdoes not have specific knowledge as to which one is currently beingused. In one embodiment, the AT tries each potential PL packet size.Note that smaller packet lengths tend to reduce loss as less informationis retransmitted if not correctly received. Similarly, there is a betterchance of decoding at lower data rates. In addition, the time taken totransmit the shorter packets (in case of no early termination) is afraction of that required for longer packets given identical channelconditions.

[0040] Multi-valued data rate requests are sent via the DRC data raterequest, wherein the correspondence is given in Table II. Thedesignation “(L)” indicates an extended PL packet length. The data ratevalues 19.2 kbps, 28.2 kbps, and 57.6 kbps, each refer to the bit lengthas given in FIG. 10, respectively. For example, DRC0 corresponds to 19.2kbps and 25.6 kbps. For data transmissions having a nominal data rate of19.2 kbps, the PL packet contains 152 bits and is transmitted over 4slots. For data transmissions having a nominal data rate of 25.6 kbps,the PL packet contains 280 bits and is transmitted over 6 slots. When afull length, or extended length packet is used, the indicator (L) isincluded in the table entry. For example, DRC5 corresponds to 307.2kbps, wherein the PL packet length is 2048 bits. Similarly, DRC7corresponds to 614 kbps, wherein the PL packet length is 2048 bits.TABLE II DRC data rate rate rate rate rate request (kbps) (kbps) (kbps)(kbps) DRC0 19.2 25.6 — — DRC1 19.2 25.6 25.6 (L) — DRC2 19.2 25.6 57.6 76.8 DRC3 19.2 25.6 57.6 153.6 DRC4 25.6 57.6 307.2 — DRC5 25.6 57.6307.2 (L) — DRC6 57.6 614.4 — — DRC7 57.6 614 (L) — —

[0041] Generally, packet division multiplexing is available when a DRCdata rate request indicates a data rate greater than or equal to 153kbps, or another predetermined value. For multiplexing, a single PLpacket of 1024 bits or more is composed of one or more MAC layercapsule(s). Each capsule then contains MAC layer packets to one or moreusers. In one HRPD system, each access probe enables a pilot(I-channel), which functions as a preamble. According to one embodiment,a modified preamble includes an Explicit Data Rate Indicator (EDRI). Theencoder packets support multiplex of data into one packet. At higherdata rates, the preamble includes an EDRI field on the modulation phaseQ branch. The EDRI is (8,4,4) bi-orthogonal coded and block repeated 8times. The EDRI specifies one of a plurality of rates. To check if apacket is for a given user, the user will check the MAC layeridentifiers. For a single user packet, the preamble transmits the MACindex on the I-branch. The MAC index (assigned to a given terminal bythe AN) is a 6-bit number used by the AN to Walsh cover the packet (withthe corresponding 64-ary Walsh cover) to aid the AT in identifyingpackets directed to thereto. This mechanism is used for a unicastpacket. For multi-user packets, the preamble transmits the EDRI on the 0-branch, wherein all users with DRC compatible with EDRI attempt todecode the packet.

[0042] Potential data rates and corresponding EDRI Length (in chips) aregiven as: 153.6 k (256), 307.2 k-L (256), 307.2 k(128), 614 k-L (128),921 k (128), 1.2M-L (128), 614 k (64), 1.2M (64), 1.5 M (128), 1.8M(64), 2.4M (64), 3.0M (64), and are further illustrated in FIG. 11. FIG.11 lists the set of data rates that are compatible with each DRC. A datarate is said to be compatible with a DRC, if the packet corresponding tothat data rate may be reliably decoded by any user capable of decoding(reliably) a packet with that DRC. Generally, the data rate compatiblewith a DRC is at most equal to that of a packet associated with thegiven DRC, and the duration of the packet is at least as long as that ofa packet associated with the given DRC. In other words, if the user candecode a packet for that DRC it can decode a packet with all the datarates that are compatible with that DRC.

[0043] For multiplexed packets, and specifically for multi-user packets,an ACKnowledgement (ACK) indicator is provided for MAC layerretransmission, referred to as D-ARQ. The ACK is transmitted on theReverse Link by those users able to decode the PL packet, wherein thepacket contains a MAC layer packet or subpacket addressed thereto. TheACK transmission is boosted by 3 dB to allow for On-Off keying. The ACKis indicated by the presence of a signal and the NACK by the absence ofthe signal. In bi-polar keying, ACK and NAK are indicated by transmitteddifferent signals, of equal strength and opposite sign relative to eachother. In contrast, with on-off keying, one of the messages (ACK) isindicated by transmitting a non-trivial signal, while the other message(NAK) is indicated by transmitting no signal. ON-OFF signaling is usedfor ARQ of multi-user packets, while bipolar signaling is used for ARQof single-user packets. For single user packets, i.e., unicasttransmission, the ACK is transmitted two slots after transmission of thepacket, i.e., in the third time-slot. This is done so as to allow timefor demodulation and decoding of the packet by the AT. For multi-userpackets, the ACK is transmitted at a time slot, which is delayed by 4slots from that of the single user packet. When a multi-user packet isdirected to a first AT, and the AN does not receive an ACK from that AT,the AN will not send a unicast packet to that AT during the next slot onthe same interlace offset. This is to disambiguate the meaning of theACK that is sent on the 7^(th) slot after the transmission of themulti-user packet.

[0044] Referring again to the packet construction procedures describedhereinabove, in a first example of packet encapsulation illustrated inFIG. 12, the SL packet is 240 bits. The SL packet is a Format A packet,the target PL packet is 280 bits, and the MAC ID=8. The SL packet isprocessed by adding two fields: SPID and LEN, as described hereinabove.The LEN field is 2 bits and the SPID field is 6 bits, resulting in amodified packet of 248 bits. An Inner CRC (8 bits) is appended, and inaddition a 16-bit CRC plus an 8-bit tail are added resulting in a 280 PLpacket. In a second example, illustrated in FIG. 13, two 240-bit SLpackets are multiplexed to form a 528-bit PL packet. A first SL packet200 is 240 bits and has a MAC ID=8. The SL packet 200 is a Format Apacket from a first user. The SL packet 220 is a Format B packet from asecond user. The SL packet 220 is also 240 bits, but has a MAC ID=5. Themultiplexed packet then includes an SPID and LEN for each of packets 200and 220. An inner CRC (8 bits), a CRC (16 bits), and a tail (8 bits) areadded to the multiplexed packet resulting in a PL packet of 528 bits. Ina third example, four same format packets, e.g., Format A packets, eachfrom different users, are multiplexed into a 1024-bit PL packet asillustrated in FIG. 14. Each SL packet has a corresponding MAC ID value.The SL packets are of various lengths, including a first SL packet of488 bits, a second SL packet of 240 bits, and two SL packets of 112bits. A SPID and LEN are applied to each SL packet to form a multiplexedpacket. An inner CRC, CRC and Tail are then applied to the multiplexedpacket to form a PL packet. In this example, a format field, FMT, isalso included. As indicated in Table 1 given hereinabove, the FMT valueidentifies the PL packet as a multiplexed packet. In a fourth example,illustrated in FIG. 15, different format packets, e.g., Format A andFormat B packets, are multiplexed to form a 2048-bit PL packet. A firstSL packet has 1000 bits, wherein the second and third SL packets are 488bits each. The first SL packet 300 is used to generate a first capsule,and the second and third packets 320, 340 are used to generate a secondcapsule. The SL packet 300 is 1000 bits and therefore may compose asingle capsule. The SL packets 320, 340 are less than 1000 bits and aretherefore one capsule includes both packets. As illustrated, a FMT andcapsule address is applied to the first SL packet 300 to form a firstcapsule. The second capsule is multiplexed capsule including the SLpackets 320, 340. To each of the SL packets 320, 340 are added an SPIDand LEN. A second capsule address is then provided for the secondcapsule. The second capsule address is cleared indicating that data formultiple recipients are included in the capsule. The two capsules arethen concatenated and a pad, CRC, and tail appended to form a 2048-bitPL packet. FIG. 18 illustrates a wireless infrastructure element 400,including transmit circuitry (Tx) 402, and receive circuitry (Rx) 418coupled to a communication bus 420. A DRC unit 410 receives the DRC datarate request as received on the DRC channel from ATs. The element 400further includes a Central Processing Unit (CPU) 412 and a memory 406.The PL packet generation 404 receives the DRC data rate request from DRCunit 410 and composes the PL packet. The PL packet generation 404 maygenerate a simplex packet or a multiplex packet, and further mayimplement any of the methods described hereinabove. FIG. 19 illustratesan AT 500 according to one embodiment. The AT 500 includes transmitcircuitry (Tx) 502, and receive circuitry (Rx) 518 coupled to acommunication bus 520. A DRC unit 510 determines the maximum data rateand transmits the corresponding request on the DRC channel from ATs. Theelement 500 further includes a Central Processing Unit (CPU) 512 and amemory 506. The PL packet interpretation 504 receives the PL packet formthe AN and determines if any content is directed to AT 500. Further thePL packet interpretation 504 determines the transmission rate of thereceived PL packet. The PL packet interpretation 504 may process asimplex packet or a multiplex packet, and further may implement any ofthe methods described hereinabove.

[0045] As described hereinabove, methods and apparatus are providingmulti-user packets on a forward link in order to improve packingefficiency. In one embodiment, shorter packets are provided to userseither in poor channel conditions or users that require smaller amountsof data due to the applications and the corresponding Quality of Service(QoS) requirements. In another embodiment, a mechanism for supportingmulti-user packets in the context of 1 xEV-DO system provides for amodified Preamble structure (Unicast v/s multi-user packets), a modifiedRate Set, and/or a modified mechanism for identifying ACK from asingle-user packet or a multiplexed packet (delayed ACK). ON/OFF keyingfor ACK channel v/s bi-polar keying used in IS-856, and/or amulti-valued interpretation of DRC

[0046] Those of skill in the art would understand that information andsignals may be represented using any of a variety of differenttechnologies and techniques. For example, data, instructions, commands,information, signals, bits, symbols, and chips that may be referencedthroughout the above description may be represented by voltages,currents, electromagnetic waves, magnetic fields or particles, opticalfields or particles, or any combination thereof.

[0047] Those of skill would further appreciate that the variousillustrative logical blocks, modules, circuits, and algorithm stepsdescribed in connection with the embodiments disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. Skilled artisans may implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the present invention.

[0048] The various illustrative logical blocks, modules, and circuitsdescribed in connection with the embodiments disclosed herein may beimplemented or performed with a general purpose processor, a digitalsignal processor (DSP), an application specific integrated circuit(ASIC), a field programmable gate array (FPGA) or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

[0049] The steps of a method or algorithm described in connection withthe embodiments disclosed herein may be embodied directly in hardware,in a software module executed by a processor, or in a combination of thetwo. A software module may reside in RAM memory, flash memory, ROMmemory, EPROM memory, EEPROM memory, registers, hard disk, a removabledisk, a CD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such the processorcan read information from, and write information to, the storage medium.In the alternative, the storage medium may be integral to the processor.The processor and the storage medium may reside in an ASIC. The ASIC mayreside in a user terminal. In the alternative, the processor and thestorage medium may reside as discrete components in a user terminal.

[0050] The previous description of the disclosed embodiments is providedto enable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for an access terminal, comprising:receiving a Physical Layer (PL) data packet including a sub-packet;extracting a sub-packet identifier; determining if the sub-packet isdirected to the access terminal; and processing the sub-packet ifdirected to the access terminal.
 2. The method as in claim 1, furthercomprising: extracting a length value indicating a bit length of aMedium Access Control (MAC) data packet corresponding to the PL datapacket.
 3. The method as in claim 2, wherein the length value identifiesa format of the PL data packet.
 4. The method as in claim 1, furthercomprising: extracting a capsule address indicating a destination of atleast one capsule in the PL data packet.
 5. The method as in claim 4,wherein the capsule address is included in a capsule address field, andwherein a designated capsule address indicates a multi-user PL datapacket.
 6. The method as in claim 1, further comprising: sending anacknowledge indicator if the sub-packet contained in the PL packet isdirected to the access terminal.
 7. A remote station apparatuscomprising: a control processor for executing computer-readableinstructions; memory storage device for storing computer-readableinstructions; and Physical layer (PL) packet interpretation unit adaptedto: determining if the sub-packet is directed to the access terminal;and processing the sub-packet if directed to the access terminal.
 8. Aremote station, comprising: means for receiving a Physical Layer (PL)data packet; means for extracting a sub-packet identifier; means fordetermining if the sub-packet is directed to the access terminal; andmeans for processing the sub-packet if directed to the access terminal.9. An Access Network apparatus comprising: Data Rate Control (DRC) unitfor receiving data rate requests from Access Terminals (ATs); andPhysical Layer (PL) packet generation unit adapted to receive the datarate requests from the DRC unit and generating a variable length PLpacket in response.
 10. The AN as in claim 9, wherein the PL packetgeneration unit is adapted to: generate a variable length Security Layer(SL) packet.
 11. The AN as in claim 10, wherein the PL packet generationunit is adapted to: combine a plurality of SL packets into one PLpacket.
 12. The AN as in claim 9, wherein the AN is adapted to:retransmit the variable length PL packet after a first number of timeslots, wherein the AN waits sufficient time slots to allow a recipientto acknowledge receipt.
 13. The AN as in claim 12, wherein the firstnumber of time slots is four.
 14. The AN as in claim 9, wherein the PLpacket generation unit generates the variable length PL packet as afunction of the data rate requests.
 15. The AN as in claim 9, whereinthe PL packet generation unit is adapted to: generate a capsulecomprising a plurality of Security Layer (SL) packets directed tomultiple Access Terminals (ATs).
 16. The AN as in claim 15, wherein thePL packet generation unit is adapted to: generate a plurality ofcapsules, wherein each capsule has a corresponding capsule address. 17.A method for processing data packets in a wireless communication system,comprising: receiving a plurality of packets for transmission to aplurality of users; concatenating a first of the plurality of packetsfor a first of the plurality of users to a second of the plurality ofpackets for a second of the plurality of users; and transmitting thefirst and second packets into one physical layer packet.
 18. A methodfor processing data packets in a wireless communication system,comprising: receiving a first block of data for transmission;determining a security layer packet size based on the size of the firstblock of data; generating a security layer packet having the determinedsecurity packet layer size.
 19. The method as in claim 18, wherein thewireless communication system has a default security layer packet sizein bits, and the determined security packet layer size is smaller thanthe default security layer packet size.
 20. The method as in claim 18,wherein determining the security layer packet comprises: determining aforward link channel condition; and determining a security layer packetsize as a function of the forward link channel condition.
 21. The methodas in claim 18, wherein determining the security layer packet rises:determining a Quality of Service (QoS) requirement; and determining asecurity layer packet size as a function of on the forward link channelcondition.
 22. A method for processing data in a wireless communicationsystem, comprising: eceiving a data rate request per a Data Rate Control(DRC) channel; electing one of a plurality of data rates correspondingto the data rate request; and ransmitting data at the selected datarate.